Process for hardening waterproofing artificial gut produced from animal fibrous material



Patented Dec. 21, 1937 UNITED STATES a p 2,l03,l38

PROCESS FOR HARDENING WATERPROOF- ING ARTIFICIAL GUT PRODUCED FROMANIMAL FIBROUS MATERIAL Oskar Walter Becker, Heidelberg, and Emil Weiss,Weinheim, Germany, assignors to Naturin G. m. b. H., Weinheim, Germany,a'company of Germany No Drawing. Application October 10, 1936, Se-

eral No. 105,145. In Germany October 15, v

Claims. A (CI. 18-57) the hide may be replaced by heat disintegration orbiological loosening or opening up, supplemented by mechanicalresolving. The resulting l5 "artificial gut is dried, for example bytreatment with hot air, and rendered waterproof in a suitable manner,for example with the aid of distillate of cellulose-containingsubstances such as wood, or formaldehyde solutions.

When carrying out the aforesaid process the waterproofing of theartificial gut offered considerable diificulties. Hardening withformaldehyde solutions frequently gives rise to insufficientlyresistantsausage cases or skins, which for ex- 'ample do not stand up to theusual boiling test sure of 0.15 atmosphere at 90 C. for minutes).

Moreover in the formalin-hardening process a large portion of theformaldehyde remains adher- 30 ing to the artificial gut, which issubsequently hardened and damaged thereby.

On the other hand the process of waterproofing artificial gut withdistillates of cellulose-containing substances, such as wood and thelike, yields very non-uniform products. In many cases excessivehardening of the artificial gut, manifested in increased brittleness andfriability, takes place. In other cases non-hardened gut is obtained,which is not sufficiently waterproof. In all cases the artificial gutfails to-stand up to the boiling test.

Exhaustive investigations have now shown that the waterproofness orresistance to boiling attained depends substantially on the composition7 of the hardening liquid. It was found that the hardening properties ofthe distillates of cellulosecontaining substances are due not only totheir content of formaldehyde, but also to their content of otheriodine-consuming substances. Whereas the formaldehyde content can bedirectly determined, the content of other hardening constituents isexpressed in terms of the iodine value. The term iodine value is hereused in the usual manner to indicate the quantity of iodine expressed ingrammes which is consumed.

(capability of resisting an internal excess presby gms. of liquid underthe conditions of Romijns iodometric method of determining formaldehyde(Ullmann, Enzyklopadie der techmschen Chemie, 2nd edition, vol. 5,(1928) page 424). The result of the hardening process also dependssubstantially on the hydrogen ion concentration of the hardening liquid.

According to this invention it has been found that uniform artificialgut, which is neither overnor under-hardened, may be obtained bytreating the artificial gut with hardening liquids, preferablydistillates of cellulose-containing substances, which have been adjustedto a formaldehyde content of from 0.025 to 0.2%, preferably 0.1 to0.15%, an iodine value of from 3.5 to 8.5, preferably 5.9, and a pHvalue of from 2.5 to 3.0.

According to this invention it was further found that certaincompensations may be eifectedin the Thus,

composition of the cellulose derivatives. too. low iodine values of thedistillates may be compensated by increasing the formaldehyde content. H

The iodine-consuming substances in the wood distillates employed withthe exceptionof formaldehyde can only be determined with difficulty.

They may, however, be replaced by compounds known per se which occur indistillates of cellulosic substances, such as coniferyl alcohol,eugenol, acetaldehyde, pyrocat-echol, pyrogallol, quinone and others.However these substances also are only sufficiently active if they areemployed in quite definite combination with formaldehyde and formic acidor acetic acid and with quite definite pH values so as to producemixtures which fulfil the hereinbefore indicated directions with regardto formaldehyde content, iodine value and pH value.

The process of this invention is with advantage carried into effect byfirst drying the artificial gut discharging from the annular nozzle.This may be effected by conveying the gut in the form of a continuousband through drying channels in which it is subjected to the action ofhot air.

Preferably air is blown from the nozzle head into the interior of thetube being formed and the artificial gut dried in this inflatedcondition. The hardening is likewise with advantage effected whilst theendless tube is in this inflated condition.

For the production of the hardening liquid cellulose-containingsubstances, particularly wood and waste products of wood, for examplesawdust, are subjected to distillation. The crude distillate obtained,which is in general more highly oxidized than the distillate obtained inthe carbonization of wood, contains up to 0.5% of formaldehyde and hasan iodine value of about 42.5. The crude distillate after a distillationis if necessary adjusted by the addition of water to a formaldehydecontent. of, for example, 0.12%, whereby the iodine value is alsodecreased. If the iodine value of the diluted distillate amounts to lessthan 3.5, crude distillate is added thereto until the iodine valueexceeds 3.5. In this case the formaldehyde content may be allowed toexceed the value indicated above. Alternatively a wood distillate may beadded, the iodine value of which is very high in proportion to theformaldehyde content, for example 1. The distillate is thereafteradjusted to pH values of between 2.5 and 3.0 by the addition of formicacid or acetic acid, if it is too alkaline and by the addition ofammonia if it is too acid.

The continuous artificial gut is painted-over or the distillate withregard to iodine value and formaldehyde content and amounts to from 2 to30 days. After this period of action the gut is washed or rinsed withwater having a pH value of 8, whereby it first becomes cloudy and thenglassy. The excess portion of the hardening substances is washed awaythereby. The gut is then again dried.

When employing distillates as aforesaid uniform products are obtained,which, with regard to strength and waterproofness, fulfil all re-.quirements demanded of artificial gut. Artificial gut as aforesaid couldbe subjected for half an hour and longer at an internal excess pressureof up to 0.2 atmosphere to temperatures of about C. without bursting.

Examples 1. Artificial gut produced from animal fibrous material, forexample in accordance with French patent specification No. 723,066,.istreated by repeated spraying with a distillate prepared as follows:

By distilling moist saw dust, a distillate is obtained, litres of whichcontain 0.5% of formaldehyde and which has an iodine value of 26.5. Tothese 100 litres there are added 317 litres of water. .The iodine valuenow amounts to 6.4 and the formaldehyde content to 0.12%. This dilutedsolution amounting to 417 litres has a pH value of 3.1 and is adjustedby the addition of 282 gms. of formic acid to a pH value of 2.68.

The gut after treatment with the distillate is dried and kept for threedays at 25 C. The gut is then washed for about 3 hours with'water havinga pH value of 8 and is then again dried.

2. Artificial gut produced in accordance with French patentspecification No. 766,016 is treated with a hardening liquid prepared asfollows:

200 gms. offormic acid-(50%), 83.5-gms. of formaldehyde (30% by weight)and 1015 gms. of pyrocatechol are dissolved in 100 litres of water. Theiodine value amounts to 8.5, the formaldehyde content to 0.025% and thepH value to 2.7.

After five-times spraying with this hardening liquid andsubsequentdrying, the gut is stored for 14 days at 25 C. and 70% relative airmoisture and is thereafter freed from the excess of the V artificial gutwith hardening liquids containing from .025 to 2% of formaldehyde, andiodine consuming substances occurring in the distillates of cellulosecontaining substances, said hardening liquids having an iodine value offrom 3.5 to 8.5

and arm value of from 2.5 to 3.0.

2. A process according to claim 1, wherein distillates ofcellulose-containingsubstances are employed as hardening liquids.

3. A process according to claim 1, wherein distillates of wood areemployed as hardening liquids.

4. A process according to claim 1, wherein mixtures of iodine-consumingsubstances occuring in the distillates of cellulose containingsubstances, formaldehyde and formic acid are employed as hardeningliquids.

5. A process according to claim 1 wherein mix tures of iodine-consumingsubstances occuring in the distillates of cellulose containingsubstances, formaldehyde and acetic acid are employed as hardeningliquids.

6. A process according to claim 1, wherein dried artificial gut ishardened.

7. A process according to claim 1, wherein the artificial gut ishardened in the form of a continuous band.

8. A process according to claim 1, wherein the artificial gut ishardened in an air-inflated condition.

9.; A process according to. claim 1, wherein the artificial gut isrepeatedly treated with the hardening liquid and dried between eachhardening treatment.

10. A process according to claim 1, wherein the artificial gut isrepeatedly treated with the hardening liquid and dried between eachhardening treatment andafter the last hardening treatment.

OSKAR WALTER BECKER. EMIL WEISS.

